Stabilization of organic compounds



Patented June 29, 1954 Ralph B. Thompson, Hinsdale,

and Joseph A.

Chenicek, Bensenville, Ill., assignors to Universal Oil Products Company, Chicago, 111., a

corporation of Delaware No Drawing. Application September 2.9, 1959, Serial No. 118,716

1 23 Claims.

This invention relates to the stabilization of organic compounds which tend to deteriorate in storage or in use due to oxidation reactions.

Various organic compounds are unstable in storage or during treatment and form undesirable gums, undergo discoloration, form sludges or otherwise deteriorate due to oxidation, polymerization or other undesired reactions. Ineluded among the organic compounds which undergo such deterioration are gasoline, diesel oil, mineral oil, lubricating oil, fuel oil, drying oil, greases, edible fats and oils, acetylenes and particularly vinyl acetylene, butadiene, isoprene, styrene and other vinyl aromatics, various unsaturated alcohols, acids, ketones, etc.

The invention is particularly applicable to the stabilization of unsaturated ,gasolines and par-- ticularly cracked and polymer gasoline-s. In storage or during treatment these unsaturated gasolines tend to form undesirable gums. The invention is also applicable to the treatment of aviation gasolines which tend to undergo deterioration due to the addition of tetraethyl lead fiu-id or due to other components in the gasoline.

The invention is also particularly applicable to the stabilization of edible late and oils which generally are of animal or vegetable origin and which tend to become rancid, especially during long periods of storage prior to use. Typical representatives of these edible fats and oils include linseed oil, menhaden oil, cod li-ver oil, castor oil, olive oil, rapeseed oil, coconut oil, palm oil, corn .oil, sesame oil, peanut oil, babassu oil, butter, zf-at, lard, beef tallow, etc. It is understood that other oils and fats may :be treated with-in the scope of the present invention, including oils and fats which previously have been subjected to various treatments, such as blowing with air, heat treatment, hydrogenation, etc.

In another embodiment the present invention is particularly applicable to the treatment of crops by dusting or spraying in order to preserve food accessory factors such as carotene, vitamins, various fatty acids, alcohols, etc.

In one embodiment the present invention relates to a method of stabilizing an organic oompound subject to 'oxidative deterioration-which comprises adding thereto an inhibitor comprising a 'tricyclic compound, containing the naphthalene ring system having fused to one of its 2 benzene rings, by a carbon atom and a heterocyclic oxy en atom, a member of the group consisting of dihydro turan and dihydro pyran rmgs,

nd the other benzene ring of said naphthalene ring having a hydroxy group attached thereto.

in the subsequent disclosure of specific compounds, the system of numbering is in conformity with the following;

In a specific embodiment the present invention relates to a method of stabilizing motor fuel normally tending to deteriorate in storage which comprises adding thereto from about 0.001% to about cart by W ght of 2,2-dimethv1 6-hydr0xv- 2,3 -dihydronanhtho- I 1,2 -;b) -furan.

In another specific embodiment the present invention relates to a method of stabilizing edible fats and oils against rancidity which comprises adding thereto from about 0.001% to about 0.5% by weight of z;2-dimeth yl-fi-hydroxy-2,3dihydronaphtho-(L2-b) -furan.

In another embodiment the present invention relates to Organic compounds normally tending to deteriorate in storage, and particularly motor fuel and edible fats and oils, containing a small amount of the inhibitors herein set .forth.

It will be noted that thenovel inhibitors of the present invention are characterized in containing a hydroxy group attached to one of the benzene rings of the .naphthalenering system and a Luz-an or pyran group attached to the other benzene ring of the naphthalene ring system. This configuration is a ,novel contribution in the field of stabilization and difiers from prior investigations which were directed to the -preparation of inhibitors from hydroquinone or dihydroxynaphthalenes containing two hydroxy groups on the same benzene ring. In viewof the unpredictability in chemical reactions-oi" this category, a oompound was prepared from:dihydroaynaphthalene containmg 'hydroxy groups difterent benzene 3:. rings and it was found that this compound is a very potent and highly satisfactory inhibitor for the stabilization of organic compounds.

The novel inhibitors of the present invention Hydroxy-2,3-dihydronaplitho- (1,2-b)-furan Hydroxy-3,4-dihydronaphtho- I E-(1,2-b)-pyran Hydroxy-l,2-(lihydronaphtho- ;3E-(2,l-b)-pyran Where R comprises hydrogen .or alkyl radicals. When R comprises alkyl;radicals, they preferably are selected so that the total number of carbon atoms in the inhibitor does not exceed about 25. Still more particularly, the 'alkyl radicals preferably contain from 1 to about 4 carbon atoms and include such groups as methyl, ethyl,

propyl and butyl.

In the preferred method ofpreparing .the inhibitor, as will hereinafter be set forth in detail, the inhibitor will contain two methyl'radicals in the 2- or 3- positions and, therefore, the inhibitors of the present invention have been so illustrated in the general structures. However, it is understood that B may comprise hydrogen and also that alkyl groupsfmaybe attached to either one or both of the'benzene ringsor to the other carbon atom or atoms'of the heterocyclic ring. In some cases these inhibitors may contain other substituents such as aryl, cyclohexyl, etc. radicals attached thereto but'it is understood that the resultant compounds are not necessarily equivalent. In generaL'the' addition of further hydrocarbon groups tendstolessen the potency of the inhibitor but,-in some cases, it may be desirable for the purpo'sejof increasing solubility in a particular substrate.

Structure I illustrates a hydroxy dihydronaphtho-(l,2-b)-furan in which the hydroxy group is attached to the benzene ring different from the one to which the heterocyclic ring is fused. Particularly satisfactory inhibitors .of this class inelude such compounds as 2,2-dimethyl-6-hydroxy-2,3-dihydronaphtho- (1,2-b) -furan, 2,2-dimethyl-'7 hydroxy-2,3-dihydronaphtho-(1,2-b)

furan, 2,2-dimethyl-8-hydroxy-'2,3-dihydronaph- I tho-(1,2-b) -furan, andf.2,2:dinithyl-9-hydroxy- 2,3-dihydronaphtho-(l,2eb)'-furan. These inhibitors are readily prepared in the manner to be hereinafter set forth by.v starting with the desired clihydroxynaphth'alene selected from the group consisting of 1,-edihydroxynaphthalene, 1,G-dihydroxynaphthalene, 'l, 7-dihydroxynaphthalene and 1,8-dihydroxynaphthalene.

Structure II illustrates a .hydroxy-dihydronaphtho- (1,2-b) -pyran having a hydroxy group attached on the benzene ring different from that to which the pyran group is fused. Particularly satisfactory inhibitors of this class include such compounds as 2,2-dimethyl-7-hydroxy-2,3-dihy dronaphtho (1,2-b) -pyran, 2,2-dimethyl-8-hydroxy-2,3-dihydronaphtho- (1,2-b) -pyran, 2,2-dimethyl-9-hydroXy-2,3-dihydronaphtho- (1,2-b) pyran and 2,2-dimethyl-l0-hydroXy-2,3-dihydronaphtho-(l,2-b) pyran. These inhibitors similarly may be prepared by starting with the desired dihydroxynap-hthalene.

Structure III illustrates a hydroXy-dihydronaphtho(2,lb)-furan having a hydroxy group attached on the benzene ring diiiereri t from the one to which the furan ring is fused. Particularly satisfactory inhibitors of this class include such compounds as 2,2-dimethyl-7-hydroxy-l,2- dihydronaphtho-(2,1b) -fur an and 2,2-dimethyl 8 hydroxy 1,2 dihydronaphtho (2,1-b) furan. These inhibtors are readily prepared by starting with the desired dihydroxynaphthalenes selected from 2,6-dihydroxy or 2,7-dihydroxynaphthalene.

Structure IV illustrates a hydroxy-dihydronaphtho-(2,1-b) -pyran having a hydroxy group attached on the benzene ring different from that to which a pyran group is fused. Particularly satisfactory inhibitors of this class include such compounds as 3,3-dimethyl-8- hydroxy-l,2 -dihyclronaphtho-3H-(2,l-b) pyran and 3,3-dimethyl- 9-hydroxy-1,2-dihydronaphtho-3H-(2,1-b) pyran. These inhibitors similarly may be prepared by starting with the desired dihydroxynaphthalene.

It is understood that the inhibitors of the present invention may comprise the specific compounds named herein in admixture with various isomers thereof. For example, the isomers may comprise corresponding compounds in which the hydroxy group and furan or pyran rings have interchanged positions with respect to the hydroxy group. Thus, with an unsymmetrical dihydroxynaphthalene, such as 1,6-, the pyran or furan rings may involve either the 1- or 6-hydroxy group.

As further examples of isomeric compounds which may be formed and used in accordance With the present invention, when starting with 1,6-dihydroxynaphthalene, the inhibitor may comprise 2,2-dimethyl-6-hydroxy-1,2 dihydronaphtho-(2,l-b) -furan. When starting with 1,7- dihydroxynaphthalene, the inhibitor may comprise 2,2-dimethyl-9-hydrcxy1,2-dihydronaphtho-(2,1-b) -furan. This same situation applies in connection with the pyrans and the inhibitor may comprise 3,3-dimethyl-7-hydroxy-1,2-dihydronaphtho-3H-(2,1-b)-pyran or 3,3-din1ethyll0 hydroxy 1,2 dihydronaphtho-3H-(2,1-b) pyran. As hereinbefore set forth, it is understood that the inhibitor may comprise a mixture of these isomers.

The inhibitors of the present invention may be prepared in any suitable manner. In a preferred method, the desired dihydroxynaphthalene, selected from the groups hereinbeiore set methanol, and water.

The reaction of the diyhdroxynaphthalene with allyl halide is readily efiected in'the presence of a basic reagent such as sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Usually the reaction is effected in the presence of a solvent, a' particularly satisfactory solvent comprising a mixture-of an alcohol, and particularly It is understood that any other suitable solvent may be employed. A particularly suitable method for eflecting this reaction, which is relatively simple and produces satisfactory results, is to heat and reflux the dihydroxynaphthalene and allyl halide in the presence of the basic reagent and solvent while stirring vigorously. The temperature of heating and refluxing, will depend upon the specific halide employed and generally will be at the boiling point temperature of the halide under the particular pressure employed. The time of refluxing should be sufficient to complete the reaction and will vary with the particular halide, dihydroxynaphthalene and type of refluxing apparatus employed. It is preferable to eiiect this reaction in an inert atmosphere such as nitrogen in order to minimize undesired color formation and side reactions. The concentration of reactants used and the time Of reaction will be selected to effect primarily the reaction of 1 mol of allyl halide with 1 mol of dihydroxynaphthalene to produce the desired monoether and to minimize formation of the diether. However, some diether will be formed in the reaction and will be removed in the manner to be hereinafter set forth. After the reaction has been completed to the desired extent, the products are cooled and extracted with an alkali to remove the desired monoether from the diether which is insoluble in alkali. The monoether is then recovered by acidification and extraction with an organic solvent. 7

The monoallyl ether is rearranged to the alkenyl dihydroxynaphthalene by heating to a boiling temperature. The rearrangement reaction is exothermic and in some cases it may be necessary to employ means to control the exothermic heat of reaction. This may be accomplished by the use of external cooling means or by ellecting the heating in the presence of a high boiling material which will not adversely affect the reaction. Suitable high boiling materials include such organic compounds as dimethylaniline, diethylaniline, coal tar base fractions boiling in the order of 220-240 C., etc. Preferably, the reaction is efiected in the presence of nitrogen. After the reaction has proceeded to the desired extent, the high boiling material may be removed in any suitable manner such as by extraction with dilute acidic solution, such as dilute hydrochloric acid, and ring closure is effected by boiling in the presence of a suitable acid such as 90% formic acid. The acid is then removed by distillation and the product is purified by distillation in vacuum. The other naphtho furans may be prepared in substantially the same manner by varying the starting reagents as desired.

2,2 dimethyl-7-hydroxy-2,3.dihydronaphtho- (1,2-b) -pyran may be prepared by warming a suspension of 1,5-dihydroxynaphthalene and isoprene in a suitable solvent, such as glacial acetic acid which has been saturated with anhydrous hydrogen chloride. After the reaction has proceeded to completion, the product is extracted with an organic solvent, such as ether-petroleum ether, and the acetic acid is removed by treatment with a suitable base such as sodium bicarbonate. The unreacted starting material may be removed by extraction with a dilute aqueous caustic solution and the final product may be purified by distillation under vacuum.

When it is desired to add other allryl group or groups to either one or both of the benzene rings, it may be effected in any suitable manner. For example, eutylation may be effected by dissolving the naphtho furan or pyran in acetic acid and adding thereto a suitable catalyst such as 85% phosphoric acid. Tertiary butyl alcohol is then added and the mixture may be heated to a temperature of (SO-85 C. with constant stirring, after which the product may be poured into water, extracted first with organic solvents and then with Claisen solution and finally distilled in vacuum.

The inhibitor of the present invention is generally added to organic materials in an amount of less than 1% by weight and generally within the range of from about 0.001% to about 0.5%. When used in gasoline, it is understood that the inhibitor may be used in conjunction with various dyes, metal deactivators, anti-knock agents such as tetraethyl lead, etc. When used in edible fats and oils it is understood that the inhibitor may be used in conjunction with a synergist, such as phosphoric acid, ascorbic acid, etc.

The following examples are introduced to further illustrate the novelty and utility of the present invention but not with the intention of unduly limiting the same.

2,2 dimethyl6hydroxy-2,3-dihydronaphtho- (1,2-b)-furan was prepared as follows: 160 grams of l,5-dihydroxynaphthalene was added to 250 cc. of methanol, .350 cc. of Water and 15 grams of sodium hydrosulfite. 182 grams of methallyl chloride was gradually added, and the mixture was vigorously stirred and boil d und: reflux conditions for 2 hours. The mi: "e allowed to cool and a liter of water, along i sufficient sodium hydroxide to form product, was added. The product was with ether-petroleum ether solvent to s the alkali insoluble diallyl diether. The al all soluble product, the desired monoetl'ier, was recovered by acidification. The monoether was boiled for hour in diethylaniline in a nitrogen atmosphere to rearrange the men-nether to 2-methallyl 1,5 dihydroxynaphthalenc. he product was extracted with dilute hydrochloric acid to separate the diethylaniline, and ring closure was effected by boiling with 90% for acid. The 2,2-dimethyl-6hydroxy-2,3di naphtho-(l,2-b) -furan distilled at 130-42:- 3 mm. Hg pressure.

Example I The following run was made with a lard which had a normal stability period of hours as determined by the Swift test. This test is described in detail in the article by A. E. 1-1. L. Roschen, and W. H. Irwin, which ap, in the Oil and Soap, vol. X, No. 6, 109 (1933). In general, this test comp bling air through a sample of the lard porting the number of hours until the lard velops a peroxide value of 20.

0.02% by weight of the 2,2-dimethyl-6-hydroxy-2,3-dihydronaphtho-(1,2-b) furan, prepared in the manner hereinbefore set forth, was added to a sample of the lard and served to increase the stability period thereof from 2% hours to approximately 6'? hours.

red to Example II This example illustrates the effectiveness of the 2,2-dimethyl-6-hydroxy-2,3 dihydronaphtho-(1,2-b) -furan as an inhibitor in gasoline. The gasoline used in this run was a Pennsylvania cracked gasoline which had an uninhibited induction period of 100 minutes. 0.05% by weight of the 2,2-dimethyl-6-hydroxy-1,3-dihydronaph tho-(1,2-b) -furan was added to a sample of this gasoline and served to increase the induction period thereof from 100 minutes to 965 minutes.

We claim as our invention:

1. An organic material normally tending to deteriorate in storage due to oxidation containing an inhibitor comprising a hydroxy-dihydronaphtho-(l,2-b) -furan in which said hydroxy group is attached to the benzene ring different from the one to which the furan ring is attached, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

2. An organic material normally tending to deteriorate in storage due to oxidation containing an inhibitor comprising a hydroxy-dihydronaphtho-(2,l-b)-furan in which said hydroxy group is attached to the benzene ring different from the one to which the furan ring is attached, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocar bon radicals.

3. An organic material normally tending to deteriorate in storage due to oxidation containing an inhibitor comprising a hydroxy-dihydro naphtho-(1,2b)pyran in which said hydroxy group is attached to the benzene ring different from the one to which the pyran ring is attached, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

4. An organic material normally tending to deteriorate in a storage due to oxidation containing an inhibitor comprising a hydroxy-dihydronaphtho-(2,1b)-pyran in which said hydroxy group is attached to the benzene ring different from the one to which the pyran ring is attached, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals" selected from the group consisting of hydrogen and hydrocarbon radicals.

5. A motor fuel normally tending to deteriorate in storage containing from about 0.001 to about 0.5% by weight of 2,2-dimethyl-6-hydroxy-l,2- dihydronaphtho-(2,1b) -furan.

6. Edible fats and oils containing from about 0.001% to about 0.5% by weight of 2,2-dimethyl- 6hydroxy-2,3-dihydronaphtho- (1,2-b) -furan.

7. Edible fats and oils containing from about 0.001% to about 0.5% by weight of 2,2-dimethyl- 6hydroxy-1,2-dihydronaphtho- (2,1-b) -furan.

8. A motor fuel normally tending to deteriorate in storage containing from about 0.001% to about 0.5% by weight of 2,2-dimethyl-7-hydroxy3,4- dihydr-onaphtho-ZH- (1,2-b) -pyran.

9. A motor fuel normally tending to deteriorate in storage containing from about 0.001% to about 0.5% by weight of 3,3-dimethyl-7-hydroxy-1,2-dihydronaphtho-3H-(2,1-b) -pyran.

10. An organic material normally tending to deteriorate in storage due to oxidation containing, as an inhibitor for said deterioration, a small amount of a tricyclic compound containing a naphthalene ring system having fused to one of its benzene rings, by a carbon atom and a heterocyclic oxygen atom, a member of the group consisting of dihydro furan and dihydro pyran rings, the other of said benzene rings in said naphthalene system having a hydroxy group attached thereto, and in which the carbon" atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

11. An organic material tending to deteriorate in storage due to oxidation containing, as an inhibitor for said deterioration, a small amount of an inhibitor comprising a hydroxy-dihydronaphtho-(1,2-b)-furan, in which said hydroxy group is attached to the benzene ring different from the one to which the furan ring is attached, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

12. An organic material tending to deteriorate in storage due to oxidation containing, as an inhibitor for said deterioration, a small amount of an inhibitor comprising a hydroxy-dihydronaphtho-(1,2-b) -pyran, in which said hydroxy group is attached to the benzene ring different from the one to which the pyran ring is attached.

13. Motor fuel subject to oxidative deterioration containing, as an inhibitor for said deterioration, from about 0.001% to about 0.5% by Weight of 2,2-dimethyl6-hydroxy-2,3-dihydronaphtho- (1,2-b) furan.

' 14'. Edible fats and oils normally tending to become rancid in storage containing, as an inhibitor for said rancidity, from about 0.001% to about 0.5% by weight of a 7-hydroxy-2,3-dihydronaphtho-(1,2-b) -pyran, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

15. A tricyclic compound containing a naphthalene ring system having fused to one of its benzene rings, by a carbon atom and a heterocyclic oxygen atom, a member of the group consisting of dihydro -furan and dihydro pyran rings, the other of said benzene rings in said naphthalene system having a hydroxy group attached thereto, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and by drocarbon radicals.

16. Mono hydroxy 2,3 dihydronaphtho- (1,2-b) -furan in which the hydroxy group is attached to a benzene ring different from the benzene ring to which the furan group is fused.

17. A hydroxy-1,2-dihydronaphtho (2,1-b)- furan in which the hydroxy group is attached to a benzene ring different from the benzene ring to which the furan group is fused, and in which the carbon atoms of the heterocyclic ring not fused to the naphthalene nucleus are substituted only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals.

18. A hydroxy-3,l-dihydronaphtho (1,243)- pyran in which the hydroxy group is attached to a benzene ring different from the benzene ring 9 10 to which the pyran group is fused, and in which References Cited in the file of this patent the carbon atoms of the heterocyclic ring not UNITED STATES PATENTS fused to the naphthalene nucleus are substituted Number Name Date only by radicals selected from the group consisting of hydrogen and hydrocarbon radicals. 5 2283388 Paul May 1942 19. 2,2-dimethyl 6 hydroxy 2,3 dihyclro- 2,320,746 e J1me 1, 1943 t z 2,362,479 Gibbs NOV. 14, 1944 7 y y y Thompson et a1. May 29, naphtho-(1,2-b)-furan. OTHER REFERENCES fg f hydroxy 1,2 dihydm' Chem. Abst. 19, page 828 (1925).

22. 2,2 dimethy1 7 hydroxy 2,3 dihydro Ber. der Deut. Chem. Ges. 81, pages 224-235 (1935). naphtho- (1,2-b) -pyran.

23. 3,3-dimethyl 8 hydroxy 1,2 dihydronaphtho-3I-I- (2,1-b) -pyran. 15 

1. AN ORGANIC MATERIAL NORMALLY TENDING TO DETERIORATE IN STORAGE DUE TO OXIDATION CONTAINING AN INHIBITOR COMPRISING A HYDROXY-DIHYDRONAPHTHO-(1,2-B)-FURAN IN WHICH SAID HYDROXY GROUP IS ATTACHED TO THE BENZENE RING DIFFERENT FROM THE ONE TO WHICH THE FURAN RING IS ATTACHED, AND IN WHICH THE CARBON ATOMS OF THE HETEROCYCLIC RING NOT FUSED TO THE NAPHTHALENE NUCLEUS ARE SUBSTITUTED ONLY BY RAIDCALS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND HYDROCARBON RADICALS. 